<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>time</title>
    <style type="text/css">
        .{
            padding: 0;margin: 0;
        }
        .box{
            width: 400px;height: 400px;border: 1px black solid;
        }
        .bo{
            whidth:100px;height: 100px;border:1px red solid; margin: 10px 10px;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="one bo"></div>
        <div class="two bo"></div>
        <div class="three bo"></div>
    </div>
</body>
</html>